Field of the Invention
The invention relates to a method for filling two containers of a system, in particular for filling a fuel tank and a reducing-agent tank surrounded by the latter. The invention also relates to a device for carrying out the method.
Exhaust-gas purification systems operated with a reducing agent have been developed in the course of the development of ever more environmentally friendly internal combustion engines. A system of that kind is known, for example, from a Siemens Company Prospectus entitled "SiNOx Nitrogen Oxide Reduction for Stationary Diesel Engines", Order No. A96001-U91-A232, Siemens AG, Berlin and Munich. That document relates to a system which is based on an SCR (Selective Catalytic Reduction) method. That method makes use of the effect whereby nitrogen oxides or urea are converted into nitrogen and water through the use of suitable catalysts. For that purpose, exhaust gases are led through the SCR catalyst, which is integrated into an exhaust-gas line, at the same time as an accurately metered addition of a reducing agent.
In an exhaust-gas purification system which is operated with a reducing agent and which cooperates with an internal combustion system supplying exhaust gas, for example with a diesel engine in a motor vehicle, it is necessary for the reducing agent to be stored in a storage container, tank or reducing-agent space. That space has heretofore been disposed at some distance and separately from the fuel space, which is provided for storing the fuel for the internal combustion system. In that case, a solid reducing agent such as urea, for example, is dissolved in a liquid, for example in water, inter alia, for reasons of good meterability. Reducing agent solutions of that kind crystallize and solidify at temperatures below which those prevailing in the vehicle, and if the reducing-agent tank is installed externally, may fall. For example, a 32.5% urea/water solution solidifies at -11.degree. C. A frozen or solidified solution can no longer be conveyed, and in such a case the exhaust gas is not purified.
Particularly in the case of a vehicle in which such an exhaust-gas purification system operated by reducing agent is employed, there is a need to accommodate the storage container for the reducing agent. German Published, Non-Prosecuted Patent Application DE 197 29 003 A1 recently proposed to place the storage container for the reducing agent within a fuel tank belonging to the internal combustion system. In that case, spatially separated filler orifices which are independent of one another are provided for filling the storage container and the fuel tank. Storage tanks from which fuel and reducing agent are pumped are normally installed spatially at a distance from one another. Two refueling operations that are independent of one another are therefore necessary in order to refuel an internal combustion system of the above-mentioned type.